WO2001096436A1

WO2001096436A1 - Polyurethane compositions based on polyester block copolymers

Info

Publication number: WO2001096436A1
Application number: PCT/EP2001/006127
Authority: WO
Inventors: Michael Krebs; Christoph Lohr; Andreas Brenger; Ingolf Scheffler
Original assignee: Henkel Kommanditgesellschaft Auf Aktien
Priority date: 2000-06-10
Filing date: 2001-05-30
Publication date: 2001-12-20
Also published as: DE10028810A1; EP1290056A1; EP1290056B1; US20030144454A1; US6906148B2; DE50111044D1

Abstract

The invention relates to compositions containing the reaction products of a polyisocyanate and a polyester block copolymer, and to a method for producing them. The inventive compositions are suitable for use as moisture-hardening hot-melt-type adhesives. The hot-melt adhesive composition can also contain a reaction product of a polyisocyanate and a polyesterpolyol and/or a reaction product of a polyisocyanate and a polyetherpolyol. Polyurethane-hot-melt adhesive compositions of this type have good creep resistance and interfacial bonding values on plastics, as well as very high strength values.

Description

"Polyurethane compositions based on polyester block

copolymers "

The invention relates to compositions containing reaction products of a polyisocyanate with a polyester block copolymer and their use as a hot melt adhesive and a process for their preparation.

Reaction products of a stoichiometric excess of polyisocyanates with polyols - so-called polyurethane prepolymers with isocyanate end groups - are used in a large number of areas, for example as sealants, coating materials or adhesives. If these compositions are solid at room temperature and can be melted in the absence of moisture in the heat or heat, they can be used as reactive hot melt adhesives. For the purposes of this invention, reactive one-component polyurethane hotmelt adhesives are moisture-curing or moisture-crosslinking adhesives which are solid at room temperature and are applied in the form of their melt as an adhesive, and whose polymeric components contain urethane groups and reactive isocyanate groups. By cooling this melt over the application to the substrate and further cooling the melt through the substrate parts, a rapid physical setting of the hot-melt adhesive takes place first through its solidification, followed by a chemical reaction of the isocyanate groups still present with moisture from the environment into one cross-linked infusible adhesive.

In principle, reactive hotmelt adhesives based on isocyanate-terminated polyurethane prepolymers are known, as HF Huber and H. Müller describe in "Shaping Reactive Hotmelts Using LMW Copolyesters", Adhesives Age, November, 1987, pages 32 to 35, the combination of isocyanate - Terminated amorphous and crystalline polyesters, which are said to have good adhesion to a wide variety of substrates, and formulations which contain isocyanate-terminated polyester block copolymers are not disclosed. EP-A-340906 describes polyurethane hot-melt adhesive compositions containing a mixture of at least 2 amorphous polyurethane prepolymers, which are characterized in that the prepolymers have different glass transition temperatures. Such mixtures of two prepolymers are said to improve the properties of the adhesive in such a way that they set quickly, are still flexible immediately after setting and have good heat stability after curing.

DE-A-3827224 describes rapidly setting, moisture-curing hotmelt adhesives from reaction products of polyisocyanates and hydroxypolyesters. The hydroxypolyesters are preferably purely aliphatic and have at least 12 methylene groups in the polyester unit composed of diol and dicarboxylic acid. Ether diols, ie oligomeric or polymers based on ethylene glycol or 1,4-butanediol, may also be present as diols, but this is not preferred.

EP-A-455400 describes a mixture of isocyanate-terminated polyurethane prepolymers which essentially consists of a first crystalline prepolymer based on polyhexamethylene adipate and a second prepolymer based on polytetrametylene ether glycol. These compositions are said to have very good adhesion to a variety of surfaces.

EP-A-568607 describes a mixture of isocyanate-terminated polyurethane prepolymers containing a first prepolymer based on the reaction product of an at least partially crystalline polyester polyol and a polyisocyanate and a second prepolymer based on the reaction product of a poly (tetramethylene ether) glycol and a polyisocyanate and a third prepolymer based on the reaction product of an amorphous polyester polyol and a polyisocyanate. The amorphous polyester polyol for the third prepolymer should preferably be composed at least in part of aromatic building blocks. In order to improve the cohesive strength of the hot melt adhesives, the molecular weight, in particular the glassy polyester polyols should be as high as possible. However, this results in extremely high viscosity polymers that are difficult to mix and difficult to mix

Application temperature are to be applied. It is stated that this

Hot melt adhesives are particularly suitable for bonding polymeric substrates such as polystyrene or polymethyl methacrylate.

WO 9115530 describes moisture-curing polyurethane hotmelt adhesives which combine the properties of thermoplastic hotmelt adhesives and reactive adhesives. Mixtures of a thermoplastic elastomer based on a polyester-polyether copolymer and a polyisocyanate prepolymer are described. The thermoplastic elastomer should be a segmented thermoplastic elastomer with hard and soft segments and the polyisocyanate prepolymer should be the reaction product of a polyois with a polyfunctional isocyanate with an isocyanate functionality of 2 or more. A preferred polyol for the polyurethane prepolymer is poly (tetramethylene ether) gycol. It is stated that these adhesives are suitable for bonding glass, metal and a number of plastics.

The as yet unpublished DE-A-19961941.7 describes compositions containing reaction products of a polyisocyanate with a polyester-polyether copolymer, a process for their preparation and their use as reactive hotmelt adhesives. There it is proposed to produce these copolymers from carboxyl-terminated polyester building blocks and polyether polyols. Although these hot melt adhesives already meet many technical requirements for modern hot melt adhesives, they cannot be used in a number of areas

Despite the extensive state of the art, there is still a need for improved polyurethane compositions that are suitable for use as hot melt adhesives. In particular, the raw materials used for the hot melt adhesives should be easily and inexpensively accessible. Better compatibility of the individual polymer components is desirable for problem-free application. In addition, the hot melt adhesives are said to be broad Adhesion spectrum to a variety of substrates and the highest possible level of strength after curing.

The solution to the problem according to the invention can be found in the patent claims. It essentially consists in the provision of a polyurethane composition for use in hot melt adhesives containing a reaction product of a polyisocyanate with a polyester block copolymer of the formula (I)

HO - R ² - O - A - O - R ¹ - OH (I)

where A = - R ³ - - C (O) - R ⁴ - C (O) - X— R ³ -,

R ¹ and R ² independently of one another (- (CH ₂ ) 4-0- (CH ₂ ) ₄ -) o, (-C ₃ H6-OC ₃ H6-) o, (-

C ₂ H -OC ₂ H4-) _p , the rest of a polybutadiene, polycarbonate or one

Are polycaprolactones or a combination thereof,

X + R ³ together form a covalent bond or X = O and R ³ = - (CH ₂ ) _m - and

R ^{4 is} a radical of a carboxyl-terminated polyester from a C to C ₁ 2 -diol and a Cβ to Cu-dicarboxylic acid after removal of the terminal carboxyl groups and is = 4 to 12, o = 5 - 80 and p = 5 - 80.

The radical of a hydroxyl-terminated polyester is preferably composed of aliphatic dicarboxylic acids and difunctional aliphatic alcohols. Preferred examples of aliphatic dicarboxylic acids are adipic acid, pimelic acid, suberic acid, azelaic acid, sebacrylic acid, undecanedioic acid, dodecanedioic acid or optionally their. Mixtures. Preferred examples of difunctional aliphatic alcohols are butanediol, hexanediol, octanediol, decanediol, dodecanediol or, if appropriate, mixtures thereof. Especially dicarboxylic acids and diols with an even number of carbon atoms are preferred.

Particularly preferred hydroxy-terminated polyester building blocks are polyester building blocks made from adipic acid, sebacic acid or dodecanedioic acid and 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol or 1,12-dodecanediol. The polyester block can have a molecular weight between 1000 and 10000, the molecular weight is preferably between 1500 and 8000. R ¹ and / or R ² are blocks composed of polyetherols such as poly (oxytetramethylene) glycol, also called poly-tetrahydrofuran (poly-THF) , Poly (oxyalkylene) glycols such as poly (oxyethylene) glycol, poly (oxypropylene) glycol, poly (oxybutylene) glycol or their copolymers, and polybutadiene, polycarbonate or polycaprolactone, the latter being particularly preferred. In principle, R ¹ and / or R ^{2 can} also be a further block of a polyester which contains building blocks other than the polyester block -OAO-. If the polyether block consists of poly-THF, the molecular weight should be between 250 and 6000, preferably between 600 and 4000. If the polyether block consists of poly (oxyalkylene) glycols, it has a molecular weight between 1000 and 6000, preferably between 1000 and 4000. In the case that R ¹ and / or R ^{2 is} polycaprolactone, the molecular weight of this block is between 80 and 4000, preferably between 500 and 4000.

The copolymer of formula (I) can be prepared by condensation of a corresponding carboxyl-terminated polyester with a polyetherol, hydroxy-functional polybutadiene, polycarbonate diol or another polyester diol. In the case of the block copolymer containing polycaprolactone, a hydroxy-functional polyester is assumed and caprolactone is polymerized. In principle, however, it is also possible to produce such a copolymer by condensing the individual components polyether polyol, aliphatic dicarboxylic acid and difunctional alcohol in a single condensation step. A preferred embodiment of the polyester block copolymer according to the formula

(I) consists of a central polyester block consisting of hexanediol adipate or a polyester based on dodecanedioic acid and hexanediol or octanediol and a polymerized on one or both sides of the hydroxyl groups

Polycaprolactone produced, that is, this is a

Reaction product of a polyester polyol with caprolactone. The

Polycaprolactone block can have a molecular weight of 80 to 4000. The entire block copolymer according to formula (I) then has one

Molecular weight between 1000 and 15000, preferably between 2500 and

8000. Also in the event that R ¹ and / or R ^{2 is} a polyether block

Polybutadiene block, another polyester block or a polycarbonate block, the above ranges apply analogously to the molecular weights.

The hydroxyl numbers of the polyester block copolymers according to the invention are in the range between 7.5 and 112, preferably between 14 and 45. This corresponds to a molecular weight range from 1000 to 15000, preferably from 1500 to 8000. The mass fraction of R ¹ and / or R ² blocks to the polyester block -OAO- between about 5 and 300%.

A large number of aliphatic, cycloaliphatic or aromatic polyisocyanates can be used as polyisocyanates.

Examples of suitable aromatic polyisocyanates are: All isomers of tolylene diisocyanate (TDI) either in isomerically pure form or as a mixture of several isomers, naphthalene-1,5-diisocyanate, diphenylmethane-4,4'-diisocyanate (MDI), diphenylmethane-2,4 ' -Diisocyanate and mixtures of 4,4'-diphenylmethane diisocyanate with the 2,4'-isomer or their mixtures with higher-functionality oligomers (so-called raw MDI), xylylene diisocyanate (XDI), 4,4'-diphenyl-dimethylmethane diisocyanate, di- and tetraalkyl diphenylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate. Examples of suitable cycloaliphatic polyisocyanates are the hydrogenation products of the aforementioned aromatic diisocyanates such as e.g. 4,4'-dicyclohexylmethane diisocyanate (H ₁₂ MDI), 1-isocyanatomethyl-3-isocyanato-1, 5,5-trimethyl-cyclohexane (isophorone diisocyanate, IPDI),

Cyclohexane-1,4-diisocyanate, hydrogenated xylylene diisocyanate (H1 ₃ XDI), 1-methyl-2,4-diisocyanato-cyclohexane, m- or p-tetramethylxylene diisocyanate (m-TMXDI, p-

TMXDI) and dimer fatty acid diisocyanate. Examples of aliphatic polyisocyanates are tetramethoxybutane-1,4-diisocyanate, butane-1,4-diisocyanate, hexane-1,6-

Diisocyanate (HDI), 1,6-diisocyanato-2,2,4-trimethylhexane, 1,6-diisocyanato-2,4,4-

Trimethylhexane and 1,12-dodecane diisocyanate (Ci ₂ DI).

The polyurethane hot-melt adhesive compositions according to the invention can optionally contain further prepolymers in the form of reaction products of one of the above-mentioned polyisocyanates with a polyester polyol and / or optionally a reaction product of one of the above-mentioned polyisocyanates with a polyether polyol as an admixture component.

Examples of such polyester polyols are reaction products of dicarboxylic acids, such as glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, 3,3-dimethylglutaric acid. Propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, 1, 10-decanediol, 1,12-dodecanediol, dimer fatty alcohol, diethylene glycol, triethylene glycol or mixtures thereof. Possibly. The suitable polyester polyols can also be slightly branched, ie minor amounts of a tricarboxylic acid or a trifunctional alcohol, for example glycerol or trimethylolpropane, have been used for their preparation. Another group of the polyester polyols to be used according to the invention are the polyesters based on ε-caprolactone, also called "polycaprolactones". However, polyester polyols of oleochemical origin can also be used. Such polyester polyols can, for example, by completely ring opening epoxidized triglycerides of an at least partially olefinically unsaturated fatty acid-containing fat mixture with one or more alcohols with 1 up to 12 carbon atoms and subsequent partial transesterification of the triglyceride derivatives to alkyl ester polyols having 1 to 12 carbon atoms in the alkyl radical. Other suitable polyols are polycarbonate polyols and dimer diols (from Henkel) and castor oil and its derivatives.

Examples of the polyether polyols to be used according to the invention for the further prepolymers are di- and / or trifunctional polypropylene glycols in the molecular weight range from 200 to 15000, preferably in the range from 400 to 4000. Statistical and / or block copolymers of ethylene oxide and polylenoxide can also be used.

The reaction of the individual polyol building blocks according to formula (I) or the further polyester polyol or the polyether polyol with the polyisocyanate is carried out in a manner known per se by converting a stoichiometric excess of polyisocyanate over the polyol compound. The stoichiometric ratio of OH groups to NCO groups is usually 1: 1.2 to 1:15, preferably this ratio is 1: 1.4 to 1: 2.5.

To prepare the isocyanate-terminated polyurethane prepolymers, it may be necessary to add known polyurethane catalysts, such as To use compounds of the tetravalent or tetravalent interest, in particular dicarboxylates of the tetravalent tin or dialkyltin dicarboxylates or dialkytin dialkoxylates.

Furthermore, it may be necessary to add catalysts to the hot-melt adhesive compositions for accelerated curing with the moisture in the environment, here in particular acycian as well as in particular cyclic amino compounds may be mentioned, examples being tetramethylbutane-diamine, bis (dimethylaminoethyl) ether, 1,4-diazabicyclooctane ( DABCO), 1, 8-diaza-bicyclo- (5.4.0) -undecene or morpholino derivatives. Examples of such morpholino derivatives are: Bis (2- (2,6-dimethyl-4-morpholino) ethyl) - (2- (4-morpholino) ethyl) amine, bis (2- (2,6-dimethyl-4-morpholino) ethyl) - (2nd - (2,6-diethyl-4-morpholino) ethyl) amine, tris (2- (4-morpholino) ethyl) amine, tris (2- (4-morpholino) propyl) amine, tris (2- (4-morpholino) ) butyl) amine, tris (2- (2,6-dimethyl-4-morpholino) ethyl) amine, tris (2- (2,6-diethyl-4-morpholino) ethyl) amine, tris (2- (2- methyl-4-morpholino) ethyl) amine or tris (2- (2-ethyl-4-morpholino) ethyl) amine, dimethylaminopropylmorpholine, bis-

(morpholinopropyl) methylamine, diethylaminopropylmorpholine, bis

(morpholinopropyl) ethylamine, bis (morpholinopropyl) propylamine,

Morpholinopropylpyrrolidone or N-morpholinopropyl-N'-methyl-piperazine, 2,2'-

Dimorpholinodiethyl ether (DMDEE) or di-2,6-dimethylmorpholinoethyl) ether

The amounts of the aforementioned catalysts to be used can vary within wide limits and depend on the type of catalyst, its activity, the conditions of use and the storage conditions required for the hot melt adhesive. For the aforementioned morpholino derivatives, in particular the particularly preferred DMDEE, catalyst concentrations between 0.0002 and 1.5% by weight, based on the total adhesive formulation, are customary.

Furthermore, the compositions according to the invention may contain further additives customary for hot melt adhesives, examples being tackifying resins, such as e.g. Abietic acid, abietic acid ester, terpene resins, terpenophenol resins or hydrocarbon resins. Furthermore, fillers can be used in minor amounts, e.g. Silicates, talc, calcium carbonates, clays, carbon black or color pastes or pigments.

The selection of the individual components, in particular the polyol components, depends on the intended use and the desired end properties. It has been found that the block structure of the polyester block copolymers of the formula (I), with appropriate selection of the block length, results in improved compatibility with hot melt adhesives based on conventional polyester polyols of the prior art, which can be seen from the fact that the hot melt adhesive according to the invention Compositions in are usually transparent in the molten state (as long as they are not

Contain fillers, pigments or similar components). Furthermore, excellent creep resistance and

Boundary surface adhesion values observed and additionally very high

Strength values achieved.

The hotmelt adhesives according to the invention are suitable for bonding a large number of substrates, in particular for bonding metallic substrates and very particularly for bonding various plastic substrates.

Examples of preferred fields of application for the hotmelt adhesives according to the invention are assembly bonding in the wood and furniture industry, clip bonding in automobile construction. In the latter application field, the clips, also called "retainers", made of ABS are glued against resin-bonded molded parts, such as those sold under the trade name "Empeflex" by Empe. Another field of application is profile wrapping in wood, furniture and window construction. PVC profiles are fully glued with PVC decorative foils.

The following examples are intended to explain the invention in more detail, the selection of the examples not restricting the scope of the subject matter of the invention. In the case of the compositions, all amounts are parts by weight, unless stated otherwise.

Examples

example 1

3600 g of a polyester (hexanediol dodecanoate, OH number 32.5 mg KOH / g; acid number 2 mg KOH / g) are placed in a reaction vessel at 120 ° C. Under a nitrogen atmosphere, 365 g of caprolactone monomer and in an amount of 1.9 g of butyltin-tris (2-ethylhexanoate) were added to the molten polyester at 120 ° C. as a catalyst. After a reaction time of 4 hours at 160 ° C., the reaction was complete. Traces remaining Caprolactone monomers were removed in vacuo. The polyester block

Copolymer had the following key figures: OH number 29 mg KOH / g; acid number

1.9 mg KOH / g, melting point 69 ° C.

Example 2

The following polyester diol and diisocyanates became reactive

Hot melt adhesive produced:

24.18 parts of amorphous copolyester based on terephthalic acid, isophthalic acid,

Neopentyl glycol, hexanediol and ethylene glycol, OH number 21, T _g 40 ° C 11, 46 parts copolyester based on adipic acid, neopentyl glycol, hexanediol and

Ethylene glycol, OH number 21, T _g -50 ° C 32.74 parts copolyester based on adipic acid and hexanediol, OH number 30,

Melting point 60 ° C 20.72 parts of polyester block copolymer according to Example 1 10.88 parts of 4,4'-diphenylmethane diisocyanate

The hot melt adhesive had the following key figures:

NCO content: 1.8%

Viscosity at 130 ° C (Brookfield Thermocell): 12000 mPa.s

With the hot-melt adhesive produced in this way, adhesion tests were carried out on various substrates and the following results were obtained:

Here mean:

WB whitening in the subsrat material

Measure of material breakage in the substrate Miss mixed break in the substrate and in the adhesive joint

PVC polyvinyl chloride

ABS acrynitrile butadiene styrene

NBR nitrile rubber cohesive break in the glue joint

Liability was assessed on the following scale: 1 = very good adhesion to 6 = very poor adhesion.

It is clear from these adhesion tests that the hotmelt adhesives according to the invention have good adhesion properties on a large number of substrates.

Claims

claims

1. Polyurethane hot-melt adhesive composition containing a.) A reaction product of a polyisocyanate with a polyester block copolymer of the formula (I)

HO - R ² - O - A - O - R ¹ - OH (I)

b.) if appropriate, a reaction product of a polyisocyanate with a polyester polyol and / or c.) if appropriate, a reaction product of a polyisocyanate with a polyether polyol

where A = - R ³ - X - C (O) - R ⁴ - C (O) - X - R ³ -,

R ¹ and R ² independently of one another (- (CH ₂ ) ₄ -O- (CH ₂ ) ₄ -) o, (-C ₃ H ₆ -OC ₃ H6-) o, (-

C ₂ H -OC ₂ H -) _p , the rest of a polybutadiene, polycarbonate or one

Polycaprolactones or a combination thereof,

X + R ³ together form a covalent bond or X = O and R ³ = - (CH ₂ ) _m - and

R ^{4 is} a residue of a carboxyl-terminated polyester from a C ₄ to C ₁₂ diol and a Cβ to C ₄ dicarboxylic acid after removal of the terminal

Mean carboxyl groups and m = 4 to 12, 0 = 5 - 80 and p = 5 - 80.

2. Composition according to claim 1, characterized in that the carboxyl-terminated polyester block A from aliphatic dicarboxylic acids selected from adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, or mixtures thereof and difunctional alcohols selected from butanediol, hexanediol, octanediol , Decanediol, dodecanediol or mixtures thereof.

3. Composition according to claim 2, characterized in that the

Polyester block has a molecular weight between 1000 and 10000, preferably between 1500 and 8000.

4. Composition according to claim 1, characterized in that R ¹ and / or R ^{2 have} a molecular weight between 80 and 15000, preferably between 600 and 4000.

5. Composition according to claim 1, characterized in that R ¹ and / or R ^{2 are} the remainder of a polycaprolactone and have a molecular weight between 80 and 4000, preferably between 500 and 4000.

6. Composition according to at least one of the preceding claims, characterized in that the polyester polyol of component b.) From aliphatic dicarboxylic acids selected from adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, dimer acid, 3,3-dimethylglutaric acid, aromatic dicarboxylic acids selected from terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid or mixtures thereof and difunctional alcohols selected from ethylene glycol, propylene glycol, butanediol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, hexanediol, octanediol, decanediol, dodecanediol, neopentyl glycol, mixtures thereof, is dimeric diol glycol, mixtures of which are phenyldiols, diophenylglycol, mixtures of which are phenyldiols, hydroxyls, diophenylglycols, hydroxyls, diophenylglycols, mixtures of which are phenyldiols, hydroxyls, diophenylglycols, hydroxyls, diophenylglycols, hydroxyls, diophenylglycols, hydroxyls, diophenylglycols, hydroxyls, diophenylglycols, hydroxyls, diophenylglycol, and their mixtures.

7. Composition according to at least one of the preceding claims, characterized in that component c.) Is a polypropylene glycol, polyethylene glycol, copolymer of ethylene oxide and propylene oxide or a poly (oxytetramethylene) glycol.

8. Composition according to at least one of the preceding claims, characterized in that it

5 to 100% by weight of component a.) 0 to 80% by weight of component b.) And 0 to 80 wt.% Of component c.) Contains.